Animal Species:Bluebottle-fish, Nomeus gronovii (Gmelin, 1789)

Young Bluebottle-fish are pelagic, but adults are demersal. The juveniles live among the tentacles of the blue bottle, Physalia,

Standard Common Name

Bluebottle-fish

Alternative Name/s

Portuguese Man-o-war Fish, Shepherd Fish

Identification

The Bluebottle-fish has a compressed body and a large forked caudal fin. The pelvic fins are large and fan-like.

Juveniles are bright blue on the back and silver on the sides. There are blue spots and blotches on the body and fins. Adults are usually dark brown.

Nomeus gronovii is only species in the genus Nomeus.

Size range

The species grows to about 26 cm in length.

Distribution

It occurs in tropical and some temperate continental shelf waters circumglobally.

In Australia, the Bluebottle-fish is known from the offshore islands of north-western Western Australia, around the tropical north of the country and down the east coast to Bass Strait, Victoria. It has also been recorded from Lord Howe Island.

The map below shows the Australian distribution of the species based on public sightings and specimens in Australian Museums. Click on the map for detailed information. Source: Atlas of Living Australia.

The Bluebottle-fish pictured was captured and kept in an aquarium for 2 days, after it which developed swimming problems and died. It was in poor condition to begin with. The rockpool it was found in also contained numerous bluebottles, as well as other Bluebottle-fish.
Some rough research revealed that this species has not been kept in aquaria succesfully. It is presumed to feed on the gonad tissue of the bluebottle.
From (rather hazardous) personal observation of this species in the wild, it appears to be immune to the bluebottle toxins.
The pictured fish is now registered in the AMS collection.
Mark: If you could put up the rego number? :-)